Numbers 4:35
From thirty years old and upward even unto fifty years old, every one that entereth into the service, for the work in the tabernacle of the congregation: From thirty years old and upward even unto fifty years old, every one that entereth into the service, for the work in the tabernacle of the congregation:
The verse describes the service of the Levites in the tabernacle of the congregation, which consisted in erecting the tabernacle and taking it down, carrying it with its sacred furnishings from place to place, and camping around it to guard and attend it. This work was appointed to the Levites by God as a distinct honor in recognition of their faithfulness. Yet the appointment conferred no right to the priesthood and no claim to the government, which remained separate from their assigned duties.